The present invention relates to a display device using ambient light and a lighting panel.
Display devices having a non light-emitting type display element, such as a liquid crystal display element, in which light projected from the outside is used and the transmission of the light is controlled for display, are classified into transmission type display devices using transmitted light and reflection type display devices, using reflected light.
The transmission type display device is a device in which a backlight is arranged at the back of the above-mentioned display element and illuminating light from the backlight is used to perform display. The illuminating light from the backlight is emitted toward the display element and then the light is emitted ahead of the display element to perform the display. In this transmission type display device, a large electric power is consumed to turn on the backlight.
The reflection type display device is a device in which ambient light (outer light), which is light in the use environment of the display device, is used for display. The ambient light incident from the front of the display element is reflected toward the display element on a reflector arranged at the back of the display element and then the light is emitted ahead of the display element to perform the display. In this reflection type display device, reflection light having an intensity according to the outer light incident from the front of the display element can be obtained. Therefore, if the device is in the environment wherein enough outer light is present, display can be observed with sufficient brightness. Any backlight is unnecessary so that a little electric power is consumed.
However, in the reflection type display device, the intensity of the reflected light that is emitted ahead of the display element greatly depends on the intensity of the outer light incident from the front of the display element. Consequently, in the environment of a high illumination over 100000 luxes, for example, in the environment under the direct rays of the sun in summer, the screen is too dazzling so that its display is hard to watch. Moreover, in dark environments, such as the open air at night, such a screen brightness in which display can be recognized cannot be obtained. Thus, the device cannot be used in the dark environments.
On the other hand, hitherto reflection type display devices having an auxiliary,light source have been proposed in order that their display can be observed in dark environments such as the open air at night.
This reflection type display device having an auxiliary light source is a device in which a semi-transmission reflector is arranged at the back of a display element and the auxiliary light source is arranged at the back of the semi-transmission reflector. As the semi-transmission reflector, a reflector having a high reflectivity and a low transmissivity is used in order to ensure a sufficiently high reflectivity of the display device (the ratio of the intensity of emitted light which is reflected on the reflector and emitted ahead of the display element to that of ambient light incident from the front of the display element).
However, in this reflection type display device having the auxiliary light source, the transmissivity of the semi-transmission reflector is very small, and the luminous brightness of the auxiliary light source cannot be made extremely high to make its consumed electric power small. Therefore, when the auxiliary light source is turned on, the brightness of the illuminating light which is transmitted through the semi-transmission reflector and projected into the display element is weak.
For this reason, in the reflection type display device having the auxiliary light source, its screen brightness is low when the auxiliary light source is turned on in dark environments. Furthermore, in the environment of an intense illumination, such as the environment under direct rays of the sun in summer, its screen is too dazzling so that its display is hard to watch.
An object of this invention is to provide a liquid crystal display element making it possible to obtain a display having a suitable screen brightness in various environments from a bright environment to a dark environment.
Another object of this invention is to provide a display device using illuminating light based on ambient light (outer light) and illuminating light based on a turned-on light source to perform display having a suitable screen brightness according to the environmental illumination in the surroundings.
In order to attain the objects, a first aspect of this invention is a display device comprising:
a non light-emitting type display element for controlling the transmission of incident light to display an image,
a light radiating unit arranged at the back of the display element for emitting illuminating light toward the display element and reflecting ambient light incident from the front of the display element at a given reflectivity toward the display element, and
an illumination brightness controller for controlling the intensity of the illuminating light so that the screen brightness of the display element comprising the total of reflected light of the ambient light reflected on the light radiating unit and transmitted light of the illuminating light is set up into a predetermined brightness range according to the reflectivity of the light radiating unit and the environmental illumination of the ambient light incident from the front of the display element.
In such a display device of the first aspect, it is possible to emit both of the reflected light of the ambient light and the transmitted light of the illuminating light ahead from the screen of the display element. At bright environmental illuminations, by adjusting the intensity of the illuminating light in accordance with the illumination of the ambient light, consumed electric power by the environmental illuminating light can be reduced, and the ambient light can be used to obtain a bright screen. At dark environmental illuminations, the screen having a sufficient brightness can be obtained by the reflected light of the ambient light and emission of the transmitted light of the illuminating light from the screen of the display element.
In the display device of the first aspect, the illumination brightness controller controls the screen brightness, according to the environmental illumination, to the brightness corresponding to curves represented by quadratic functions satisfying the following ranges:
a screen brightness of 20-200 nits at an environmental illumination of 50 luxes,
a screen brightness of 30-300 nits at an environmental illumination of 1000 luxes, and
a screen brightness of 400-4000 nits at an environmental illumination of 30000 luxes.
Desirably, the illumination brightness controller controls the screen brightness, according to the environmental illumination, to the brightness corresponding to curves represented by quadratic functions satisfying the following ranges:
a screen brightness of 20-60 nits at an environmental illumination of 50 luxes,
a screen brightness of 60-200 nits at an environmental illumination of 1000 luxes, and
a screen brightness of 1000-3000 nits at an environmental illumination of 30000 luxes.
In the display element wherein its screen brightness is controlled in such a way, even at dark environmental illuminations less than 50 luxes, a screen brightness suitable for observation can be obtained. Even at an environmental illumination of 1000 luxes, which is close to the illumination inside a room, a screen brightness suitable for observation can be obtained. Even at an environmental illumination of 30000 luxes, which is close to the illumination in the open air in the daytime, a screen brightness suitable for observation can be obtained.
In the display device of the first aspect, the illumination brightness controller controls the screen brightness, according to the environmental illumination, to satisfy:
xe2x88x922xc3x9710xe2x88x928xc3x97I2+0.015+I+20 less than L less than xe2x88x923xc3x9710xe2x88x927xc3x97I2+0.113xc3x97I+150,
wherein the environmental illumination is represented by I (luxes) and the screen brightness is represented by L (nits).
Preferably, the illumination brightness controller controls the screen brightness, according to the environmental illumination, to satisfy:
xe2x88x929xc3x9710xe2x88x928xc3x97I2+0.0453xc3x97I+20 less than L less than xe2x88x922xc3x9710xe2x88x927xc3x97I2+0.0871xc3x97I+50,
wherein the environmental illumination is represented by I (luxes) and the screen brightness is represented by L (nits).
In the display device wherein its screen brightness is controlled in such a way, a screen brightness suitable for observation can be obtained, even at dark environmental illuminations, in addition, even at an environmental illumination which is close to the illumination inside a room, and even at an environmental illumination which is close to the illumination in the open air in the day time.
In the display device of the first aspect, the illumination brightness controller controls the brightness of the illuminating light from the light radiating unit at an environmental illumination that is, at lowest, higher than the illumination inside a room, and preferably, the illumination brightness controller controls the brightness of the illuminating light from the light radiating unit in the range in which the environmental illumination is from not more than 50 luxes to more than about 30000 luxes.
In the display device wherein its screen brightness is controlled in such a way, the brightness of the illuminating light from the light radiating unit is made small at environmental illuminations more than indoor illumination, so that the electric power consumed by the illuminating light can be reduced in bright environments.
In the display device of the first aspect, the illumination brightness controller controls the brightness of illuminating light from the light radiating unit in a manner that, within the illumination range in which the environmental illumination is lower than indoor illumination, the brightness of the illuminating light is continuously lowered as the environmental illumination becomes low.
In the display element wherein its screen brightness is controlled in such a way, within the illumination range in which the environmental illumination is lower than indoor illumination, the brightness of the illuminating light from the light radiating unit is raised, in order to supplement the decrease in the brightness of the illuminating light, as the environmental illumination is reduced. Thus, a screen brightness suitable for observation can be obtained.
In the display device of the first aspect, the illumination brightness controller controls the brightness of illuminating light from the light radiating unit in a manner that, within the illumination range in which the environmental illumination is higher than indoor illumination and is not more than a given illumination, the brightness of the illuminating light is continuously raised as the environmental illumination rises and,
When the environmental illumination exceeds the given illumination, the brightness of the illuminating light is continuously lowered as the environmental illumination further rises.
In the display device wherein its screen brightness is controlled in such a way, within the illumination range in which the environmental illumination is higher than the indoor illumination and is not more than the given illumination, the brightness of the illuminating light is continuously raised to increase the screen brightness. When the environmental illumination exceeds the given illumination, the brightness of the illuminating light is continuously lowered. Thus, it is possible to adjust consumed electric power of the illumination light necessary for obtaining a sufficient screen brightness.
In the display device of the first aspect, the illumination brightness controller controls the brightness of illuminating light from the light radiating unit in a manner that:
1) within the illumination range in which the environmental illumination is lower than indoor illumination, the brightness of the illuminating light is continuously lowered as the environmental illumination becomes low;
2) within the illumination range in which the environmental illumination is higher than the indoor illumination and is not more than a given illumination, the brightness of the illuminating light is continuously raised as the environmental illumination rises,
3) when the environmental illumination exceeds the given illumination, the brightness of the illuminating light is continuously lowered as the environmental illumination further rises.
In the display element wherein its screen brightness is controlled in such a way, within the illumination range in which the environmental illumination is lower than indoor illumination, the brightness of the illuminating light is continuously lowered. Thus, it is avoided that the screen brightness becomes too bright. Within the illumination range in which the environmental illumination is higher than the indoor illumination and is not more than the given illumination, the brightness of the screen brightness is raised according to the rise in the environmental illumination. When the environmental illumination exceeds the given illumination, the brightness of the illuminating light can be reduced by the increased ambient light. Thus, consumed electric power can be reduced.
In the display device of the first aspect, the illumination brightness controller has an illumination detector for measuring the environmental illumination, and a light source brightness adjusting circuit for controlling the brightness of illuminating light emitted from the light radiating unit on the basis of the measured environmental illumination.
In the display device of a second aspect, the light radiating unit has a means for radiating illuminating light onto the display element, and a means for reflecting ambient light projected from the front of the display element and reflecting the reflected light onto the display element.
In the display device of the second aspect, the light radiating unit comprises:
1) a light source, and
2) a photoconductor in which formed are at least one end face in which the light source is arranged opposed thereto, an emitting face for guiding the illuminating light from the light source and emitting the light toward the display element, and a reflective face, which are different from the emitting face, for reflecting ambient light which is projected from the front of the display element toward the display element.
In the display device of the second aspect, the light radiating unit is composed of a light source, a photoconductor wherein the light source is arranged at least one end thereof, and an optical member arranged at the front aide of the photoconductor,
1) the photoconductor comprises an incident end face, as at least end face, for taking in illuminating light form the light source, and a front face made up to a stepwise face comprising step faces which become lower stepwise from the side of the incident end face to the other side and step-level-difference faces each of which connects the step faces,
reflective films for reflecting the ambient light are deposited on the respective step faces of the photoconductor, and emitting faces for emitting the ambient light projected from the incident end face are formed in the respective step-level-difference faces, and
2) the optical member comprises an element which is arrange at the front side of the photoconductor and is for transmitting the ambient light projected from the front of the display element and emitting the reflected light of the ambient light which is reflected on the reflective films on respective the step faces of the photoconductor and the illuminating light emitted from the respective step-level-difference faces of the photoconductor toward the display element to convert the advancing direction of the light.
In the display element having such a light radiating unit, both of the reflected light of the ambient light projected from the front of the display element and the illuminating light from the light source can be emitted ahead of the display element.
The optical member is made of a transparent plate comprising a front face, opposed to the display element, for emitting light and a back face opposed to the front face of the photoconductor, and projection-form incident portions are formed at the back face of the optical member, the incident portions having an incident face for taking in light emitted from the respective step-level-difference faces of the photoconductor and a refractive face for reflecting or refracting light taken in from the incident face toward the front.
The respective incident portion of the photoconductor are disposed to leave spaces between each other, and back areas between the adjacent incident portions are make up to incident/emitting faces for transmitting the ambient light projected from the front of the display element and the reflected light of the ambient light reflected on the reflective faces on the respective step faces of the photoconductor.
According to such a light radiating unit, it is possible to emit the illuminating light from the light source from the step-level-difference faces of the photoconductor and subsequently refract the light through the optical member so as to be supplied ahead of the display element, and further it is possible to reflect the ambient light projected from the front of the display element on the reflective faces of the respective step faces of the photoconductor to be supplied ahead of the display element.
In the display device of the second aspect, the back face of the photoconductor of the light radiating unit is made up to a light diffusing face for averaging the brightness distribution, in the width direction of the photoconductor of the illuminating light projected from the incident end face.
In the display device of the second aspect, a light diffusing film is disposed between the light radiating unit and the display element.
By disposing the light diffusing film in such a way, the reflected light of the ambient light emitted from the light radiating unit and the illuminating light from the light source can be diffused and projected into the display element. Thus, a display device having a wide visual field angle can be obtained.
In the display device of the second aspect, a reflecting polarizer is disposed between the light radiating unit and the display element. The reflecting polarizer has a reflection axis and a transmission axis crossing each other at substantially right angles and a property of reflecting incident light of the polarized component along the reflection axis and transmitting incident light of the polarized component along the transmission axis.
The display element comprises a liquid crystal display element having on each of its front and back faces a polarizer, and the reflecting polarizer is arranged so that its transmission axis is substantially parallel to the transmission axis of the polarizer at the back side of the liquid crystal display element.
In the display device wherein the reflecting polarizer having a property of transmitting one component of the polarized components crossing each other at right angles and reflecting the other is arranged in such a way between the light radiating unit and the display element, only the light ray whose direction is consistent with the direction of the transmission axis of the polarizer at the back of the display element, among the illuminating light from the light source, is transmitted through the reflecting polarizer. The other light rays are not absorbed to be scattered and reflected inside the light radiating unit.
In a display device of another embodiment according to the second aspect of this invention, the light radiating unit comprises:
1) a light source,
2) a photoconductor wherein formed are an emitting face for guiding illuminating light form the light source and emitting the light toward the display element, and a transmission face, different form the emitting face, for transmitting ambient light which is projected from the front of the display element, and
3) a back side reflecting means, at the back side opposed to the incident/emitting face of the photoconductor, for reflecting the ambient light toward the side of the transmission face of the photoconductor.
The light radiating unit is composed of a light source, a photoconductor in, which the light source is arranged at least at one end face, a back side reflective means arranged at the back side of the photoconductor, and an optical member arranged at the front side of the photoconductor,
1) the photoconductor comprises an incident end face, as at least end face, for taking in illuminating light form the light source, and a front face made up to a stepwise face comprising step faces which become lower stepwise from the side of the incident end face to the other side and step-level-difference faces each of which connects the step faces,
the step-level-difference faces are made up to emitting faces for emitting the illuminating light projected from the incident end face, and the step faces are made up to transmission faces, different from the emitting faces, for transmitting the ambient light projected from the front of the display element,
2) the back side reflecting means is disposed opposed to the step faces of the photoconductor at the back side of the photoconductor, and has reflective faces for reflecting the ambient light which is projected into the step faces of the photoconductor from the front of the display element to emit the light from the step faces, and
3) an optical member, which is arranged at the front side of the photoconductor, allows to transmit the reflected light of the ambient light projected from the front of the display element and the reflected light of the ambient light reflected on the back side reflecting means, and emit the illuminating light emitted from the respective step-level-difference faces of the photoconductor toward the display element.
The light radiating unit has an optical member, which is arranged at the front side of the photoconductor, for transmitting the ambient light projected from the front and the reflected light of the ambient light which is reflected on the back side reflecting means and emitted from the step faces of the photoconductor and emitting the illuminating light which is emitted from the step-level-difference faces of the photoconductor ahead in a given direction.
In the display device using such a light radiating unit, it is possible to emit the illuminating light from the light source from the step-level-difference faces of the photoconductor and subsequently refract the light through the optical member so as to be supplied ahead of the display element, and further it is possible to transmit the ambient light projected from the front of the display element through the transmission faces on the respective step-level-difference faces of the photoconductor and reflect the light on the back side reflecting means at the back side of the photoconductor to be supplied ahead of the display element.
In the display element of the display device of a third aspect of this invention, among a pair of substrates at the front and back sides opposed to each other through a liquid crystal layer, one substrate has on its inner face first electrodes, and the other substrate has on its inner face at least one second electrode whose portion opposite to the first electrodes are made up to pixel areas, and a color filter having a smaller area than the area of the pixel area is disposed on an interface of either of the substrate, corresponding to each of the pixel areas.
The pixel areas of the liquid crystal display element have a filter-corresponding area covered with a color filter having a smaller area than the pixel area, and a non-filter area arranged around the filter-corresponding area and not covered with the color filter.
In the display device using such a liquid crystal display element, a part of the ambient light projected from its front face is transmitted through the non-filter areas, reflected, and again transmitted through the non-filter areas, so that reflected light having a high brightness can be obtained. Furthermore, the ambient light projected from the front face of the liquid crystal display element is seldom transmitted through the respective filter-corresponding areas in the adjacent pixel areas. Therefore, the light is not transmitted through the color filters in the different colors, so that a large brightness without mixed colors can be obtained.
The display device of a fourth aspect of this invention is composed of a non light-emitting type display element, a transmission display system comprising a light radiating unit, which is arranged at the back of the display element, for emitting illuminating light toward the display element, a reflection display system for reflecting the ambient light projected from the front of the display element on the light radiating unit and emitting the light ahead of the display element, and a screen brightness compensating display system for emitting the illuminating light from the light radiating unit and compensating the screen brightness of the display element based on the reflection display system by the emitted illuminating light, wherein the reflectivity of the ambient light in the reflection display system is about 16% or more when the transmissivity of the display element is controlled to the maximum.
The reflection display system has a reflectivity of 70% when the aperture ratio of the display element is set to 100%, the display element has an aperture ratio of about 60% or more, and the reflection display system has a color filter having a transmissivity of 36%.
The reflectivity of the ambient light in the reflection display system is 20% or more.
The display device of the fourth aspect makes it possible to efficiently reflect the ambient light projected,from the front, toward the front. Thus, if the environmental illumination is more than a given illumination, a sufficient screen brightness can be obtained by only the illuminating light based on the reflected light of ambient light.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.